Sound translating device



Oct.. 13, 1942. A F. HRLACHER 2,298,754

` SOUND TRNSLATING DEVICE l Filed Jan. 2'7, 1941 f w ,NM

l l I l l .If v f INVENTOR. Albert Hor/acher BY Lm ATTORNEYS.

i `lIt isfthe principal object of the Patented 135k *A UNITED- STAT application January zr, 1941,`se`r1e1 No. 376,094

'r i OFFICE a cams. (ci inea-1.14)

invention relates to soundtranslating.,devices and more particularly to receivers forl telephone instruments.

tiontoprovide an` `improved sound translating device of the type mentioned, which is of rugged anducompactconstruction and which is `highly eiilcient in operation.` Y

another object; of the mvenuon is tprovme in oasoundtranslating device,` an improved magnetic circuit..:\which is extremely. short and of considerable cross-sectional area. Y

The objects set forth above are attained in `apr:-` cordance .with` the present invention by providing i a sound translating device comprising a cylindrical cup-shapedcasing, an annular cap secured tothe open end olfI theycasingw and an annular Ivibratory magnetic diaphragm mounted adjacent l its peripheralledge between the open end of the casing and the cap. Also,- the device comprises a i cylindrical magnetic core element disposed subi stantially centrallywlthin the casing and having a Jpole face presented to the diaphragm, aiirst ring-` e `shaped magnetic field element disposed `adjacent the open end of the casing below the diaphragm andsurrounding the core element in spaced relation therewith, the first field element `having a pole `face presented to the diaphragm, and a sec-` ond magnetic field element disposed adjacent the bottom wall ofthe casing and magnetically connected to the core element. Further the` device comprises a winding `disposed in the casing and surrounding the core-element, a substantially C shaped permanent magnet disposed in the casing and partially surrounding the winding, the permanent magnetbeingpositicned between the first ileld` element and` the second iield element arid` presenting opposite poles thereto, and a terminal block 4carried by the side wall oi the casing and projecting inwardly into the open side of` the C- shaped permanent magnet More particularly, the coreelement carries an outwardly projecting annular ledgeV presenting an annular pole face to an annular `central portion of the diaphragm remote from `theperipheral edge thereof; and the first field element carries an outwardly projecting annular ledge arranged in surrounding present `linverlportions or the diaphragm, muy the annular mtervening portion of thediaphragml disposed bee vtweenthe annular central and annular surrounding fportions thereof. The novel features believed to becharacteristic .ofthe invention are set forth with particularity in the appended claims. e The invention, both as to its organization and method of operation, to-

gether withfurther objects andadvantages thereof, will best .be understood by `reference to the following specification taken in connection with `thelaccompanying drawing, in `which Figure `1 is aplan view of a sound translating device em bodying the present invention; Fig. 2 is a transverse sectional view of the device shown in Fig. 1; and Fig.3 `is a plan view ofv the device shown in Figs. land 2, illustrating `the relative positions of theelements housedin the casing thereof when the cap, the diaphragm and the stack of damping l material incorporated therein areremoved. e

Referring now moreparticularly to the drawing, there is shown a sound translating device l0 inthe iorm of a receiver for a telephone instrue ment and embodying the present invention. The

close spaced relation with the annular ledge car-` rid by the care element and presentingan annular pole face to an annular portion of the diaphragm in surrounding. close relation with the `annular central portion thereof, whereby the principal magnetic `ilux traversing the `core elementand the field element traverses, in addition to the annular central and annular surrounding `device I0 comprises a cylindrical cup-shaped casing I I and an annular cap I2, whereby the device as arwhole has 'a thin cylindrical configuration. Both the casing II and the cap I2 are formed of insulating material, preferably Bakelite. j The casing I I comprises a bottom wall I3, an upstanding cylindrical side wall I4 and an outwardly flared annular rim I5; while the cap I2 comprises a hat top wall IE and `a downwardly turned cylindrical rim I1. The rim I1 of the cap I2 in in- `ternally threaded to receive external threads provided on the rimIS of the casing I I.

An annular magnetic vibratory diaphragm I8 is arranged between the open end of the casing i I and the cap I2, the peripheral edge of the diaphragm I8 being clamped between two cooperating annularledges I9 and 2U respectively carried by the rim` I5 of the casing I I and the top w'all I6 v .ofthe cap I2. `A shallow annular recess is provided injthe'top wall I6 of the cap I2 in order to provide aushallow chamber 2I adjacent the front side of the diaphragm I8,the chamber 2l communicating with the exterior by way of a plurality of restricted openings 22 disposed in the top wall I6of the cap I2.

A substantially cylindrical magnetic core element 23 is centrally disposed within the casing II and is provided with an outwardly projecting annular ledge 24' presenting an annular pole face to an annular central portion of the diaphragm I8 remotefrom the peripheral ,edge thereof. A

substantially ring-shaped magnetic iield .element 25 is disposed in the open end of the casing II, the field element 25 being seated in an annular recess 26 cut in the interior face of the rim I5 of the casing I I. The field element 25 is arranged in surrounding close spaced relation with the core element 23 and carries an outwardly projecting annular ledge 21 arranged in surrounding close spaced relation with the annular ledge 24 carried by the core element 23 andpresnting'an annular pole face to an annular portion of the diaphragm I9 disposed in surrounding close relation with the annular central portion thereof. An annular stack 28 of sheets of damping material is disposed between the diaphragm I3 and the field element 25 and positioned between the annular ledge I9 carried by the rim I5 of the casing II and the annular ledge 21 carried by the field element 25. Preferably, the annular stack of sheets of damping material comprises a number of layers or sheets of soft paper effective to damp the vibration of the diaphragm I8 at its natural frequency of vibration, thereby to minimize distortion of the response of the device III.

The lower end of the core element 23 is secured to a semiannular magnetic field element 29 by a magnetic screw 30.l The field element 29 is disposed adjacent the bottom wall I3 of the casing II, the position ofthe field element 29 with reference to the bottom wall I3 of the casing II being adjustable by an arrangement' including a screw 3| threaded into a tapped hole provided in the bottom wall I3 of the casing II. An insulating winding spool 32 is mounted on the core element 23 in surrounding relation therewith and carries a surrounding winding 33. Preferably, the winding spool 32 is formed of Bakelite.

A substantially C-shaped permanent magnet 34 is disposed within the casing yII in surrounding relation with respect to the Winding 33 and between the field element 25 and the field element 29, the permanent magnet 34 being positioned between the winding 33 and the cylindrical side wall I4 of the casing II'and in spaced relation with respect thereto. 'I'he permanent magnet 34 is magnetized longitudinally of the center line of the core element 23, whereby a semiannular north poler thereof is presented to.

the field element 29 and a semiannular south pole thereof is presented to the field element 25. Preferably, the permanent magnet 34 is formed of Alnico; While the core element 23 and the field elements 25 and 29 are formed of Allegheny Electric Metal.

In view of the above description of the construction and arrangement of the core element 23, the permanent magnet 34 and the field ele-` ments 25 and 29, it will be understood that the device I comprises a series magnetic circuit extending from the north pole of the permanent magnet 34 by way of the field element 29, the core element 23, the annular ledge 24 carried by the core element 23, the annular central portion of the diaphragm I8, the annular intervening portion of the diaphragm I8 disposed between the annular central portion and the annular surrounding portion thereof, the annular surrounding portion lof the diaphragm I8, the annular ledge 21 carried by the field element 25, and the field element 25 to the south pole of the permanent magnet 34. Thus, it will be understood that the magnetic flux traversing the annular ledges 24 and 21 respectively carried by the core element 23 and the field element 25 is -to minimize the reluctance of the magnetic path introduced by the diaphragm I8 and to enhance the response of the diaphragm I8 overthe operating frequency band.

Further, the device comprises a terminal block including two electrical terminal elements 35 and 36 and a supporting element 31, the terminal block being carried by the side wall I4 of the casing II and projecting inwardly into the open side of the C-shaped permanent magnet 34. More particularly, the electrical terminal elements 35 and 39 are embedded in two spacedapart openings formed in the side wall I4 of the casing II; while the supporting element 31 is embedded in a recess disposed intermediate the two spaced-apart openings and formed in the side wall I4 of the casing II. Preferably, the exterior walls ofthe terminal elements 35 and 36 are knurled; while the supporting element 31 comprises a section having a substantially L-shape, thereby positively to insure anchoring of the electrical terminal elements 35 and 36 and the supporting element 31 in the side wall I4 of the casing II. Preferably, the electrical terminal elements 35 and 36 and the supporting element 31 are hot-pressedv into the respective openings and recess formed in the side wall I4 of the casing II after the casing II has been molded and before it has been allowed to set. Finally, the electrical terminal elements 35 and 35 are respectively connected to the opposite ends, not shown, of the winding 33, thereby to afford a connection between the winding 33 and an exterior telephone' circuit,not

'casing II disposed between the opposite ends of the substantially C-shaped permanent magnet 34,

While there has been described what is at" present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein and it is intended to cover in the appended claims ail such modiilcations as fall within the true spirit and scope of the Invention.

What is claimed is:

1-. A sound translating device comprising a longitudinally extending cylindrical cup-shaped casing, a laterally extending vibratory diaphragm mounted adjacent its marginal edge in the open end of said casing, a longitudinally extending core element disposed substantially centrally within said casing and having a pole face presented to said diaphragm, a laterally extending first field element disposed adjacent the open end of said casing in substantially parallel close spaced relation with respect to said diaphragm and surrounding said core element in close spaced relation therewith, said first neld element having a pole face presented to said diaphragm, a laterally extending second fieldy element disposed adjacent the bottom end of said `casing and magnetically connected to said core element, a winding disposed in said casing and surrounding said core element, said winding being positioned between said rst neld element and said second ileld element, and a vseniiannular permanent magnet disposedin said casing and at least partially surrounding said winding, said permanent Imagnet being positioned between said first eldy field element disposed adjacent. the open end of said casing in substantially parallel spaced relation with respect to said diaphragm and surrounding said core element in close spaced relation therewith, said neld element being positioned below and closely adjacent said diaphragm and having a longitudinally projecting ledge presenting a pole face to said diaphragm, an annular stack of sheets ofidamping material disposed be` tween said diaphragm .and said tleld element. a

winding disposed in said casing and surround` ing said core element, and senil-annular permanent magnet disposed in said casing and-at' least partially surrounding said winding, said permament magnet being coupled both to said oore element and said ileld element and presenting opposite pcles thereto.

3. A sound translating device comprising a longitudinally extending cylindrical cup-shaped casing, a laterally extending vibratory diaphragm mounted adjacent its marginal edge in the open end of said casing, a longitudinally extending core element disposed substantially centrally within said casing yand having a pole face presented to said diaphragm, a laterally extending nrst tleld element disposed adjacent t'he open end of said casing in substantially parallel close spaced relation with respect to said diaphragm and surrounding said core element in close spaced relation therewith, said iirst field element having a pole face presented to said diaphragm, a laterally extending second neld element disposed adjacent the bottom end of said casing and magnetically connected to said core element, a winding disposed in said casing and surrounding said core element, said winding being positioned between said iirst ileld element and said second neld element, a substantially C-shaped permanent magnet disposed in said casing and partially surrounding said winding, said permanent magnet being positioned between said iirst element and said second ileld element and presenting opposite longitudinally spaced-apart poles theretor and a terminal block carried by the side wall of said casing and projecting laterally into the open side of said c-shaped permanent magnet.

ALBERT F. HORLACHER. 

